Project II - Repair in High Risk Newborns with Congenital Heart Disease Congenital heart disease (CHD) is the most common birth defect, and neonatal surgery is often necessary for survival. Despite the complexity of these surgeries, most infants with CHD survive. Although severe neurologic disability is rare, school age children with CHD frequently exhibit behavioral, emotional, cognitive and motor impairments. The pervasive nature of these disabilities suggests fundamental problems with brain development. Using advanced magnetic resonance imaging techniques, we have discovered that newborns with CHD have delayed brain development compared with normal babies and are at high risk of acquiring new brain injuries before and after surgery. The overall goal of this proposal is to understand neurodevelopmental impairment following neonatal CHD surgery at a structural brain network level and to determine the capacity for repair following neonatal brain injury. To achieve this goal, this study will use new techniques for analyzing the complete set of brain connections - the so-called 'connectome'. Newborns with two types of CHD will be studied before and after surgery and again at six months of age. The groups differ in the number of surgeries needed to restore heart function and blood oxygen levels to near normal levels. By performing MRIs at three time points, we will learn how development of brain networks are affected in CHD and how repair and recovery from brain injury proceeds following neonatal surgery. This information will be useful for developing new treatments to optimize brain development and recovery from brain injury in any condition where newborn brain injury occurs because of low brain oxygen and/or blood flow.